Fix Cloud Composer Сreate environment operator to validate final env state after creation

[VladaZakharova]

Fix Cloud Composer environment creation to succeed only when the environment is actually usable.

Previously, create could rely on stale state from the create long-running operation, and the AlreadyExists path could incorrectly treat an environment in a bad state as success. This PR makes the create operator verify the current environment state and fail unless it is RUNNING.

The system test retry flow is also updated to delete environments left in ERROR before retrying creation.

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[Copilot]

Pull request overview

Updates the Google Cloud Composer “create environment” operator to only report success when the environment is actually usable (i.e., in RUNNING), addressing cases where the create LRO or AlreadyExists path could otherwise allow unhealthy environments to pass as successful.

Changes:

• Re-check Composer environment state via get_environment() after create operation completion and on the AlreadyExists path; fail unless state is RUNNING.
• Extend unit tests to cover post-operation state validation, AlreadyExists behavior, and deferrable execute_complete validation.
• Update system test example + docs to add a retry cleanup callback that deletes environments left in ERROR before retrying creation.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
providers/google/src/airflow/providers/google/cloud/operators/cloud_composer.py	Adds environment state validation logic for create (sync + deferrable) and AlreadyExists flows.
providers/google/tests/unit/google/cloud/operators/test_cloud_composer.py	Adds unit coverage for new state validation behavior and error cases.
providers/google/tests/system/google/cloud/composer/example_cloud_composer.py	Adds retry cleanup callback for system-test create retries; configures retries for create tasks.
providers/google/docs/operators/cloud/cloud_composer.rst	Documents new “succeed only when RUNNING” behavior and shows retry cleanup example snippet.